The present invention relates to an engine transmission control system.
A powertrain has an engine and a transmission. A control system for a powertrain determines the target speed ratio for a transmission and the target engine torque for an engine from various input data received from the vehicle and operator. Continuously variable transmissions (CVT""s) are transmissions that change ratio continuously, not in discrete intervals. The continuous nature of CVT""s gives them an infinite number of gear ratios, making them very attractive for automotive uses.
Previously, there have been various methods to control the speed ratio of the transmission and the engine torque of the engine. The most straightforward way is to define a routine target driving force in response to various input data from vehicle and operator, and define a target engine torque and a target speed ratio to achieve the target driving force, and then adjust an operation parameter of the engine and the control valve of the transmission in manners to achieve the target engine torque and the target speed ratio.
During traveling on a ramp between a highway and a city roadway, the routine driving force cannot meet operator demand because the traffic environment on the ramp where there are no crossing and pedestrians prompts the operator to demand increased driving force.
JP-A 10-141491 discloses a method of controlling the speed ratio of the transmission during traveling on a ramp from a highway to a city roadway. The method moves the upper limit of speed ratios of the transmission in response to various input data from vehicle and operator during traveling on the ramp. According to this proposal, during traveling on the ramp, the upper limit is moved in a shift down direction upon releasing an accelerator pedal and depressing a brake pedal. The upper limit is moved back in a shift up direction upon subsequently depressing the accelerator pedal. In this case, the driving force demanded by the operator cannot be achieved because there is the tendency that the subsequent depression of the accelerator causes the transmission to shift up.
Accordingly, a need remains to improve a control system in such a direction as to meet operator demand during traveling on a ramp that connects a highway and a city roadway.
An object of the present invention is to provide an engine transmission control system, which has satisfied the above-mentioned need.
In accordance with one aspect of the present invention, there is provided a control system for an engine-transmission powertrain of a vehicle having a transmission to establish various speed ratios between input and output shafts of the transmission, an accelerator pedal with various positions including a released position, and an engine with various output torque levels, the control system comprising:
a vehicle navigation system including a map database with map information including kinds of roadways, said vehicle navigation system being operable to provide information as to a current position of the vehicle and information as to a kind of roadway which the current vehicle position is on;
a ramp detection unit operatively connected with said vehicle navigation system to determine whether or not the vehicle is on a ramp;
an accelerator pedal sensor operatively connected to the accelerator pedal to detect operator demand by detecting current position of the accelerator pedal; and
a controller, which receives output signals of said ramp detection unit and said accelerator pedal sensor, generating a command upon determination by said ramp detection unit that the vehicle is on the ramp and applying said command to the engine-transmission powertrain, affecting control of the engine-transmission powertrain to meet the detected operator demand.
In accordance with another preferred implementation of the present invention, the target window for vehicle acceleration is set during traveling on a ramp to meet operator deceleration demand.